Field
The present disclosure relates to electric fluid heaters and more particularly pertains to a new versatile encapsulated fluid heater configuration for producing encapsulation vessels with different operating capabilities with fewer unique parts.
Description of the Prior Art
Fluid heating apparatus that employ an encapsulated electrical heating element are highly useful for environments where utilizing a flame or combustion to heat the fluid is not suitable. In these types of heating apparatus, the electrical heating element is typically encapsulated or enclosed in a chamber formed by a containment vessel. The fluid passing out of the chamber is directed to the desired end use for the fluid, such as a spray gun, and fluid entering the chamber has already passed through a pump and been brought up to the pressure desired at the outlet of the apparatus. The range of pressures at which the fluid passes through the chamber may range up to 3,000 psi or more. Illustrative embodiments of encapsulated fluid heaters are disclosed in U.S. Pat. No. 6,289,177 which is assigned to the same assignee as the present application and which is hereby incorporated by reference in its entirety.
As shown in FIG. 6, prior encapsulation vessels 1 have generally included a main portion 2 which is generally tubular with a closed end, and a base portion 3 which is welded to the open end of the main portion opposite of the closed end and supports the heating elements in the chamber. A pedestal 4 of the base portion is inserted into the open end and forms a shoulder 5 for sliding the perimeter wall 6 of the main portion over prior to joining the main portion to the base portion by welding.
Due to the wide range of pressures that may be utilized in such fluid heating apparatus, the strength of the encapsulating structure must be matched to the pressures being utilized in a particular apparatus in order to avoid leakage or an explosive failure. The vessel walls are generally thicker in those apparatus that utilize higher fluid pressures and the vessel walls are relatively thinner in apparatus utilizing relatively lower fluid pressures. The walls of the vessel are constructed with a thickness that is necessary for the pressures to be generated, but are usually not thicker than the necessary wall thickness in order to minimize the weight of the vessel (and thus the overall weight of the apparatus) and minimize the expense of the materials. Typically the containment vessels use tubular structures that have about the same outer diameter to maintain compatibility of the vessels of different operating pressures with other elements of the fluid heating apparatus without significant alterations to the overall design, and the variation in wall thickness is accomplished by varying the inner diameter of the tubular structure to provide the necessary wall thickness for the specific pressure range to be used in a particular heater apparatus.